1. Field of the Invention
The present invention relates to a high frequency module suitable for a cellular phone and the like.
2. Description of the Background Art
In a conventional high frequency module, a strip line including a microstrip line is formed using a one-sided substrate, a double-sided substrate, or even a stacked layer substrate according to its purpose, and a resistor, a capacitor, and also a semiconductor component required for the circuitry are mounted on the top layer.
One example of a conventional high frequency module is shown in a schematic perspective view of FIG. 8. The conventional high frequency module has a configuration in which, as shown in FIG. 8 from the bottom, an underside shield layer 105, a substrate layer 104 in which a strip line for a resonator is formed, a ground layer 103, a top layer 102 in which a so-called chip component (a resistor, a capacitor, and other semiconductor component) is mounted, and a metal cap shield case 101 are stacked.
Due to such a configuration, the size and the thickness of the conventional high frequency module is determined by the shapes of these components. According to market demand, component manufacturers concentrate their efforts on reducing the size and the thickness of these chip components.
On the other hand, assembly manufacturers proceed with their circuit design effort by introducing special facilities and a variety of simulators in order to effect high density mounting. Under such circumstances, more compact, thinner, and lighter types of a variety of cellular phones, PDA (Personal Digital Assistants) and the like are needed. In order to meet the need, the miniaturization of the module has become indispensable.
For the conventional module, the transition is being made from the chip size of 1608 (1.6 mmxc3x970.8 mm) to the chip size of 1005 (1.0 mmxc3x970.5 mm), and in some cases, even the chip size of 0603 (0.06 mmxc3x970.3 mm) is adopted. The transition from the 1005 size chip to the 0603 size chip would involve an exponentially greater number of problems related to the unit cost of components, mounting, mounting facilities, yield, and so on.
The background art, however, is not fully prepared to achieve the compactness, the lightness in weight, and the low cost as demanded by the market as described above. Moreover, once the process technology for the 0603 size chip is established, the novel miniaturization technology to be applied to the process technology must be considered. The above-described background art would prove insufficient for such application to the process technology.
The present invention is made to solve the above problem, and its object is to provide a compact, light-weight, low cost high frequency module that facilitates design modification.
To achieve the above object, the high frequency module according to the present invention is provided with a first passive element array layer with interconnection including a plurality of first passive elements formed in an array and a first passive element interconnection pattern for providing electrical connection among the plurality of first passive elements, and a second passive element array layer with interconnection including a plurality of second passive elements formed in an array and a second passive element interconnection pattern for providing electrical connection among the plurality of second passive elements. The configuration of the present invention is characterized in that a desired circuit constant can be obtained by providing interconnections among the plurality of first passive elements or among the plurality of second passive elements in any given combination simply by modifying the first or the second passive element interconnection pattern.
One of a resistor element, a capacitor element, and an inductor element corresponds to the above first passive element. Similarly, one of a resistor element, a capacitor element, and an inductor element corresponds to the above second passive element.
In the high frequency module according to the present invention, the first passive element array layer with interconnection and the second passive element array layer with interconnection, for instance, are formed on different surfaces of the substrate or both on the same surface of the substrate. In either case, the first passive element interconnection pattern and the second passive element interconnection pattern are electrically connected by the interconnection that lies between the first passive element array layer with interconnection and second passive element array layer with interconnection.
When the first passive element array layer with interconnection and the second passive element array layer with interconnection are respectively formed on the top surface and the back surface of one substrate, the electrical connection between the first passive element interconnection pattern and the second passive element interconnection pattern is provided by a conductive layer formed in a through hole provided through the substrate.
According to the present invention, with the above-described configuration, resistor elements, capacitor elements, or inductor elements may be formed in an array of elements having a prescribed resistance value, capacitance value, or inductance value that is predetermined irrespective of the specific use to which the high frequency module is applied, and the circuit constant required for a desired use can be obtained by combining these elements by the modification of the interconnection pattern alone. Such a high module can be applied to a wide variety of uses so that it can be designed as a standard high frequency module that meets a variety of demands. This results in mass production that achieves a significant reduction in the production cost.
In addition, upon design modification, only the modification of the interconnection pattern of each array layer is required besides the modification of the circuit design so that the development time as well as the development cost can be reduced.
The formation of a resistor array, a capacitor array, or an inductor array as a passive element array for the high frequency module according to the present invention using such techniques as printing, evaporation, photo etching, and selective plating improves precision, so that a module having a desired performance characteristic can be formed, which is industrially significant.
Moreover, since a passive element in the form of a chip component is not used, there no longer is the need to handle an extremely small chip component such as the conventional 0603 size chip. Thus, expensive equipments such as a mounter become unnecessary.
Furthermore, according to the present invention, a great number of passive components can be built inside by forming them on a main surface of a substrate layer to be stacked so that only the semiconductor components that are the active components need to be mounted, on the top layer in an upper portion of the stacked body, for instance. This can be sufficiently managed by the conventional facilities.
In one preferred example of the high frequency module according to the present invention, at least one of a strip line and an active electronic component is arranged above or below, or both above and below the first passive element array layer with interconnection.
The high frequency module according to the present invention can be configured such that all of either the plurality of first passive elements or the plurality of second passive elements have the same resistance value, capacitance value, or inductance value. In addition, either the plurality of first passive elements or the plurality of second passive elements may be divided into a plurality of groups, and all the passive elements forming each group may be set with the same resistance value, capacitance value, or inductance value.
The above-described configuration becomes possible since a desired circuit constant can be obtained by providing interconnections among the plurality of first passive elements or among the plurality of second passive elements in any given combination by simply modifying only the first or second passive element interconnection pattern.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.